Hydroponic culture of Gladiolus tristis: Application of paclobutrazol for flowering and height control

Gladiolus tristis (ever-flowering gladiolus) was tested for its potential as a flowering potted plant, using the growth retardant paclobutrazol. The treatments included a control, 2, 4, 8 and 16 mg activeingredient (a.i.) per pot and were applied when the longest leaves reached 15 cm. All treatments reduced perpendicular leaf height. Inflorescence heights were significantly affected by paclobutrazol.The flower spikes of plants treated with 2, 4 and 8 mg a.i. per pot were only marginally shorter than the control, while the height of plants treated with 16 mg was significantly reduced. All plants reached firstflower anthesis within a month from 22 weeks after planting. Flowering was staggered throughout the month, from the control through to plants treated with 16 mg a.i., with the control flowering from 166days after planting, gradually increasing to 178 for 2 mg, 181 for 4 mg, 183 for 8 mg, and 186 for 16 mg a.i./pot. The average number of flowers produced per pot significantly dropped with increasing strengthof a.i. applied. The control produced an average of three flowers while plants treated with 16 mg a.i produced less than one

The performance of plant species in removing nutrients from stormwater in biofiltration systems in Cape Town

In 2009, the City of Cape Town (CoCT) adopted a stormwater policy which mandates that new and existing developments should reduce the concentration of phosphorus and suspended solids in stormwater runoff by 45% and 80%, respectively, but offered no explicit guidance about how these water quality targets might be achieved. This study aims to contribute to the limited knowledge that exists about the performance of local plant species to treat stormwater. A large nursery-based study was conducted to investigate the performance of 9 locally-occurring plant species to remove orthophosphate (PO4-3), ammonia (NH3) and nitrate (NO3-) found in urban stormwater. Synthetic stormwater was applied to each species as well as a control consisting only of soil (Malmesbury shale). The discharge was collected from a drainage pipe at the base of each of the 150 containers. The results show that all species (excluding Ficinia) reduced the average concentrations of PO4-3 by 81% and NH3 by 90%. By contrast, NO3- was reduced by an average of 69% (excluding by Elegia and Phragmites) with 8 of the 9 species removing significantly more than the control. The species that performed well for all three nutrients include Agapanthus and turf grasses, Stenotaphrum and Pennisetum. The results of the study highlight three important factors in the design of biofilters: that a substantial proportion of nutrients can be captured or absorbed by plants; that the soil medium is an important factor in the removal of PO4-3 and NH3; and that plant choice is essential in the removal of NO3-. Future research should test plant species in both the laboratory and field settings, and should include additional contaminants such as household detergents, heavy metals and bacteria